Gordon has raised the possibility of buying a lens like this used as pros upgrade to the new model. Well, the new model hasn't come out yet but that's pretty much how I got mine. I was pretty lucky but I had waited a long time and had even considered a 500mm f/4.5L. I was even luckier that the calibration was spot on and the lens works beautifully with all my bodies.

Yes, it's still a big slab of money but if you can wait (I waited 2 years) you have time to save.

I look at it this way: I know friends with hobby cars. I have friends with hobby motorcycles. I have a hobby lens which cost a lot less than what they fork out. The downside is that I'm not going on holidays in the near future!

Slightly off-topic but with the USA retiring the Shuttle and reverting to a more old-school approach (MPCV) it's good to know that, as reported here, we in Europe are pressing ahead with ground-breaking technology even though the initial iteration will, if funding continues to be forthcoming, be unmanned:

If, and OK, it's a big "if", this long talked about engine technology fulfils all its promise wouldn't you just have to feel sorry for the NASA guys if they were passed on orbit by something like the ship in the picture above while cooped up in one of these: